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• Initial report on the use of bubble-assisted sustainable EC-MXene
• Predominantly O-terminated EC-MXene maintains strong tribological behavior
• Stable tribofilm formation by EC-MXene validated by experimental evidence and DFT analysis
Reducing frictional energy losses and wear in advanced mechanical systems requires the development of environmentally sustainable solid lubricants. Among emerging candidates, two-dimensional MXenes are particularly attractive due to their weak interlayer bonding, which promotes smooth sliding and low friction. However, the widespread use of MXenes has been constrained by traditional synthesis routes that employ toxic chemicals, notably hydrofluoric acid, raising serious safety and environmental concerns.
Here, we report the first demonstration of bubble-assisted electrochemical MXene synthesis for solid lubrication applications. The resulting EC-MXene possess predominantly oxygen-based surface terminations and a substantially lower fluorine concentration than conventional MXenes. Tribological tests conducted with EC-MXene coatings on AISI 52100 steel against Si₃N₄, Al₂O₃, and steel counterfaces reveal excellent frictional performance, with the lowest and most stable coefficient of friction (≈0.25) observed for Si₃N₄ contacts.
Advanced surface and interface analyses—including SEM-EDS, Raman spectroscopy, TEM (SAED and EELS), and LEIS—demonstrate the formation of a stable tribofilm accompanied by a continuous replenishment process. This process maintains lubrication by transferring MXene flakes from material pile-up regions back into the sliding contact. Complementary DFT calculations indicate strong interfacial bonding between EC-MXene and ceramic substrates, explaining the experimentally observed friction and wear behavior. Additional load-dependent experiments highlight the critical roles of adhesion strength and tribofilm structural ordering.
Collectively, these findings identify EC-MXene as a viable, sustainable alternative to classical MXenes, combining safe synthesis with high tribological efficiency. The results position EC-MXene as a reference material for next-generation sustainable two-dimensional solid lubricants suitable for both mechanical and biotribological applications.